I also don't think Adrian Peterson will finish his career with more than 15,000 yards. There is nothing wrong with finishing short of that mark and he is a Hall of Famer, but that is a lot of rushing yards. Only three players have surpassed that total in NFL history. All three of those running backs had more rushing yards before age 30 than the 10,190 yards Peterson has accumulated.
Rushing yards before age 30(after age 30)
Barry Sanders 13,778 yards(1491 yards)
Emmitt Smith 12,566 yards(5789 yards)
Walter Payton 11,625 yards(5101 yards)
Those are the guys with over 15,000 yards. Here are a few other notable running backs.
Eric Dickerson 11,226 yards(2033 yards)
Earl Campbell 8764 yards(643 yards)
LaDainian Tomlinson 11,760 yards(1924 yards)
Curtis Martin 10,361 yards(3740 yards)
Thanks for doing this research. Good post, J.
FWIW, Sanders retired at 30 still a great player and left another 5000-6000 yards that he could have gained in 4-6 more seasons. Few doubt BS would own the record owned by ES if he did not retire early. And Campbell's running style was just too violent for him to have a longer career.
Of the 15,000 yd club, obviously Payton is judged by most NFL historians to be in the top two backs of all time (Jim Brown). And in the opinion of most experts and IMO, Emmitt and Barry were better than AP although AP is probably a better athlete than both in terms of combined speed, explosiveness, elusiveness and power.
Of the others you listed, IMO, AP is better than LT and Curtis Martin, both of whom were great backs in their own right.
Honestly, I am surprised Dickerson did not get more yards after turning 30. I think he was better than Dorsett, Simpson, Campbell and is a top five RB in NFL history (I rate him behind Payton, Brown, Gale Sayers and possibly Sanders). He was truly great and every time he touched the ball vs the Cowboys I held my breath. When he got in the open field no one - other than Darrell Green - had a chance at catching him.
AP would have between 11,000-11,500 yd if he had played the entire 2014 season.
I could be wrong - and based on history, as you point out, the odds are I am wrong - but I think AP has 5000-6000 yards left in him if he plays out his career with the Cowboys. He can break as many tackles as Murray can, and then some, and once he's past the line of scrimmage he can outrun more DBs than Murray can. With Romo throwing to Dez, Witten and Beasley, and with possibly the best run blocking OL in the league, teams could not play eight-man fronts all game and AP would see holes open up for him that were not there in MN. He didn't have Romo and he didn't have Smith, Frederick and Martin in MN. With that talent around him, and assuming he is in phenominal shape, AP could have 2-3 monster years in Dallas.